How to drive a node group in Geo Nodes Blender 2.9.3a?
It's not possible to instantiate geometry that's not tied to another object in the Point Instance node at the moment, but it is planned for a future version. It is a known limitation right now.
As a workaround you can use a collection with pre-generated objects and uncheck &quot;Whole Collection&quot;. Tweak the node seed to randomize instances. Each element of the collection should have equal chances to be instantiated. I think weights similar to the particle system settings are planned.